Seaside is a rare example of software that runs on all the major current Smalltalk platforms: Pharo, Gemstone, GNU Smalltalk, Squeak, VA Smalltalk, and VisualWorks. This presentation to the NYC Smalltalk users group looks at some of the tools and techniques the Seaside team uses to make life as easy as possible for the frameworks porters.

1. Portability in Seaside
NYC Smalltalk
December 10, 2009

2. Julian Fitzell
Co-creator of Seaside
Independent consultant

4. 694 classes

5. 6844 methods

6. Platforms

8. External Interface Support
XML Support enables XML–Smalltalk object
mapping, includes a server interface via XML
request handlers and reading of remote resources
B disk via TCP sockets using HTTP requests
OLE Support enables an application to use OLE
clients and custom control services.
Domino Connection allows an application to
retrieve and work with Domino documents as well
as access Notes mail system.
Download a risk-free trial copy:
www.instantiations.com/VAST/download
m/VAST
Build Quality Software
l other trademarks mentioned are the property of their respective owners.

9. Portability
Photo: Alexia´s, flickr.com

10. Goals
Create consistent experience
Minimize platform changes
Isolate platform changes
Ease code updates (in both directions!)

11. Namespacing:
WAObject
#seasideUrl

12. Syntax
Photo: pipp, sxc.hu

13. n o
Underscore
Assignments
a_1
b←2

14. n o
Brace Arrays
{ 1. 2. 1 + 2 }

15. n o
Array Constructors
#[ ‘string’, 123, Object new ]

16. n o
Byte Arrays
#[ 1 2 3 ]

17. n o
Variable Bindings
{Smalltalk.Object}

18. n o
Selection Blocks
{:i | i.is.permanent}

19. o k Pragma
<javascript: 1.5>

20. ANSI
Photo: njd89, sxc.hu

21. ANSI Protocols
Object, Character, Boolean, nil, etc.
Block
Exception
Numeric
Collection
Date and Time
Stream

22. Exceptions
Photo: ingythewingy, flickr.com

23. Exception Protocols
#signal, #signal:, ...
#on:do:, #ensure:, #ifCurtailed:
#defaultAction, #isResumable
#pass, #outer, #retry, #resume
Warning, Error, Notification, ZeroDivide, ...

24. n o
[ ... ]
on: Error
do: [ ... ]

25. y e s
[ ... ]
on: Error
do: [ |err| ... ]

26. n o
#defaultAction
+
non-resumable
exceptions

27. “The exact behavior and
result of this method is
implementation defined.”

28. Unless the exception is resumable,
“the action taken upon completion
of the #defaultAction method is
implementation defined”

29. n o
MyException signal

30. Collections
Photo: ijsendoorn,sxc.hu

31. Collection Protocols
Array, Set, OrderedCollection, Interval, ...
#do:, #collect:, #select:, #reject:, #detect:, ...
#includes:, #isEmpty, anySatisfy:, ...
#asSet, #asOrderedCollection, ...
#at:put:, #at:ifAbsent:, #removeKey:, ...

32. n o
Collection>>#=

33. n o
#withIndexDo:

34. y e s
#keysAndValuesDo:

35. n o
#pairsDo:

36. y e s
1
to: aCollection size
by: 2 do: [ :i | ... ]

37. Strings
Photo: Lynne Lancaster, sxc.hu

38. n o
Symbol is a String

39. n o
#match:

40. n o
Object>>#asString

41. n o
#displayString

42. n o
Non-ASCII Strings

43. Streams
Photo: Lynne Lancaster, sxc.hu

44. Stream Protocols
ReadStream, WriteStream,
ReadWriteStream
#close, #isEmpty, #position, #reset, ...
#do:, #next, #peek, #upTo:, ...
#cr, #nextPut:, #nextPutAll:, ...

45. n o
#next, at the end
of a stream

46. y e s
Check #atEnd first

47. n o
#position
#position:

48. Times
and
Dates
Photo: inya, sxc.hu

49. y e s
DateAndTime
+
Duration

50. n o
TimeStamp

51. k in d a
Time

52. s o r ta
Date

53. Cross-Platform Behaviour
Consistent
Conflicting
Missing

54. Unit
Slime Grease
Tests
Consistent Conflicting Missing
Use it! Avoid it! Add it!
(Test it!)

55. Unit Tests
Photo: shadowkill, sxc.hu

56. Done?

57. Unit Tests
150
131
44 44
20
0
Seaside 2.5 Seaside 2.6 Seaside 2.7 Seaside 2.8 Seaside 3.0

58. Unit Tests
1,200
1,115
1,050

59. Slime
Lint Tests
for Seaside
Photo: A Syed, sxc.hu

60. Rules to detect
Portability Issues

61. a _ 1.
b := { a + 2. 3 }.
c pairsDo: [ :a :b | a raisedTo: b ]

62. a _ 1.
b := { a + 2. 3 }.
c pairsDo: [ :a :b | a raisedTo: b ]

63. a _ 1.
b := { a + 2. 3 }.
c pairsDo: [ :a :b | a raisedTo: b ]

64. a _ 1.
b := { a + 2. 3 }.
c pairsDo: [ :a :b | a raisedTo: b ]

65. Rules to detect
Seaside Bugs

66. html div
with: ‘Hello World’;
id: ‘message’.
html updater
id: ‘message’;
callback: [ :r | html text: ‘Bye’ ]

67. html div
with: ‘Hello World’;
id: ‘message’.
html updater
id: ‘message’;
callback: [ :r | html text: ‘Bye’ ]

68. html div
with: ‘Hello World’;
id: ‘message’.
html updater
id: ‘message’;
callback: [ :r | html text: ‘Bye’ ]

69. Grease
Platform
Compatibility
Layer
Photo: DarkSide, sxc.hu

70. Pragmatic

71. Minimal

72. Unit Tested

73. ANSI++

74. Grease Features
Consistent object initialization
Consistent exception signalling
Common convenience methods
Platform-dependent behaviour
Unit tests

75. y e s
GRObject class>>#new
^ self basicNew initialize

76. y e s
GRError class>>#signal
“VW implementation”
^ self raiseSignal

77. y e s
Object>>#greaseString
“Squeak implementation”
^ self asString

78. y e s#trimLeft
#upToLast:
#ifNil:
#isCollection

79. y e s
GRPlatform current
base64Decode: 'aGk='.
GRPlatform current
addToStartupList: SomeClass.
GRPlatform current
openDebuggerOn: anException.

80. Packaging
↑
SUnit
Photo: Tory Byrne, www.sxc.hu

81. 73 Packages

82. Common
Seaside-Core

83. Platform-Specific
Seaside-Pharo-Core

84. Test
Seaside-Tests-Core
Seaside-Tests-Pharo-Core

85. BON US!
Find incorrect layer
dependencies

86. Monticello

87. Monticello
Declarative modeling
Distributed repositories
Optimistic code merging
Vendor round-tripping

88. Monticello
☹ Slow with large repositories
☹ Inconvenient with many packages
☹ Awkward when renaming and moving
between packages

89. Future?

90. Metacello
Declare and load package configurations
Express dependencies on other projects
Easily upgrade to newest versions

91. Mason
Automate build process
Run tests for each package + dependencies

92. Monticello2
Faster
Per-method version history
Better interface for projects with many
packages
Easier to port? (uses Grease)

93. book.seaside.st

94. Summary
Write tests!
Avoid extended syntax
Use ANSI where possible
Package out platform-specific code
Slime/Lint for what you can’t use, Grease for
what you can

95. www.seaside.st
blog.fitzell.ca
jfitzell@gmail.com